A communication system is a facility which facilitates the communication between two or more entities such as communication devices, network entities and other nodes. A communication system may be provided by one more interconnected networks. A communication device can be understood as a device provided with appropriate communication and control capabilities for enabling use thereof for communication with others parties. The communication may comprise, for example, communication of voice, electronic mail (email), text messages, data, multimedia and so on. A communication device typically enables a user of the device to receive and transmit communication via a communication system and can thus be used for accessing various service applications.
In cellular systems a network entity in the form of a base station provides a node for communication with mobile devices in one or more cells. A base station is often referred to as a ‘Node B’. There are many different techniques for processing signals for transmission between the base station and the user equipment. Typically the operation of a base station apparatus and other apparatus of an access system required for the communication is controlled by a particular control entity. The control entity is typically interconnected with other control entities of the particular communication network.
A non-limiting example of a type of access architecture is a concept known as the Evolved Universal Terrestrial Radio Access (E-UTRA), which is part of the Third Generation Partnership Project Long Term Evolution (3GPP LTE) standard. Within the E-UTRA architecture, it is proposed to use Orthogonal Frequency Division Multiple Access (OFDMA) for the downlink (i.e. base station to mobile station) and Single Carrier Frequency Division Multiple Access (SC-FDMA) for the uplink (mobile station to base station). In 3GPP systems it is proposed that, in relation to general control channel structure, there will be a division between control and data, and that both use time domain multiplexing, e.g. a number of OFDM symbols in each TTI (transmission time interval) will carry the control channels for a number of user equipments (e.g. mobile/user equipment UE) for the Physical Downlink Control Channel (PDCCH), and a set of OFDM symbols will carry the shared channel for a number of users (PDSCH).
This invention relates further improvements in LTE-Advanced systems of 3GPP and more specifically to the UL control channel design.
The LTE-Advanced system is the next major step from the LTE Rel'8 system and it fulfils the requirements of the fourth generation (4G) communication network as specified by the International Telecommunications Union (ITU). SU-MIMO with up to four transmission antennas will be supported in LTE-Advanced system.
LIE-Advanced applies Rel'8 type of physical uplink control channel (PUCCH) to transmit control signals, such as an acknowledgement (ACK)/negative-ACK (NAK), a channel quality indicator (CQI) and a scheduling request (SR) indicator, from a user equipment (UE) to an evolved node B (eNB).
As far as the UL control signalling relating to systems such as the LTE-Advanced is concerned, various schemes have been proposed. From the UL coverage point of view, single-carrier transmission is the preferable solution. However there is a problem from ACK/NAK signalling point of view by taking the component carrier (CC)-specific HARQ and transport block into account. With an assumption of CC-specific HARQ/transport block there will be a need to transmit multiple ACK/NACK bits during one UL subframe. At the same time, there will be multiple PUCCH Format 1a/1b resources being reserved (assuming CC-specific PDCCH). Each of the reserved PUCCH resources is capable to transmit at most 2 ACK/NACK bits during one sub-frame. The problem is that UE cannot transmit multiple ACK/NACK bits via multiple resources in parallel without significant PAPR increase. PUCCH signalling related to Rel'8 TDD has been discussed in the prior art. However, as mentioned it does not take into account usage of multiple PUCCH resources and multiple transmit antennas at the same time.
It is an object of the invention to optimize and arrange the PUCCH transmission in the case when the UE is employed with multiple transmit antennas and more than one PUCCH Format 1a/1b. FIG. 3 shows an example of PUCCH formats.